This application is based on and claims priority to Japanese Patent Application No. 11-98182, filed Apr. 5, 1999, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to skis for snow vehicles. More particularly, the present invention relates to steering skis having improved tracking and component cooling characteristics for such vehicles.
2. Description of the Related Art
The use of snowmobiles and similar snow vehicles has increased in popularity in recent years. These vehicles are being used both for utilitarian purposes and for sport and recreational purposes. The vehicles typically are adapted to travel across snow and/or ice and usually include one or more forward facing skis along with a driven belt track or other propulsion mechanism, such as wheels for instance.
The sport and recreational use of such snowmobiles is being practiced on groomed trails in ski resort areas, for example. On such surfaces, the snowmobiles are generally easily controlled through the use of weight shifting and steering movement of the skis. However, when the snow becomes packed and/or icy, the snowmobile may be less likely to follow the desired track through the snow. In such instances, the snowmobile may become very difficult to handle.
Snowmobile skis typically have an elongated keel that is positioned along the bottom of the ski. The keel acts to increase the bite of the ski in the snow when the ski is turned. Such keels typically leave an impression in the snow corresponding to the profile of the ski and keel. When the snow is wet or compacted, a later following snowmobile ski that happens upon an impression left by a previous snowmobile ski will tend to follow the same track. This condition is generally known as tracking or darting, and is especially prevalent if the temperature has dropped causing wet snow to freeze. Darting forces the snowmobile operator to compensate or correct for the tracking steering forces by oversteering the vehicle to maintain directional stability. This is because the keel of the snowmobile following a track left by a previous snowmobile will naturally situate itself in the previous impression and considerable effort could be required to steer out of such a track. Over time darting can cause the driver to become fatigued from the effort of steering and the handling characteristics of the snowmobile can be greatly decreased.
One solution to the darting problem is to simply increase the total width of the keel. The wide keel would promote steerability and decrease the likelihood of a later-following snowmobile from falling within a track left by the more prevalent narrower keeled snowmobile. Such an arrangement, however, suffers from some obvious drawbacks. First, should such a feature become popular, the use of a wider keel would not have the desired effect of reducing darting. Additionally, widening the keel would result in poor turning performance. This is because the ski is often made of a synthetic resin material that is easily elastically deformed. If the keel is increased in width, the keel could deform more readily and the performance of the ski would be impaired and/or compromised.
A need therefore exists for an improved steering ski. The ski should be capable of reducing darting while also being capable of long-term usage with minimal maintenance. Preferably, the ski would include a reinforcing runner that would be designed to increase the cutting or carving effect of the ski during turning. Additionally, a forward portion of the runner should extend down below the body of the ski such that the wear bar can increase the cutting or carving ability of the ski when in use. Such an arrangement would result form the reinforcement added by the more rigid wear bar relative to the more flexible ski body.
One aspect of the present invention involves a ski for a snowmobile comprising a body having a substantially horizontal snow contact section and an upturned forward leading portion. A tip is defined at a forward-most end of the leading portion. The leading portion and the snow-contacting portion meet at a junction. A keel depends downward from the body and the keel increases in width from the tip to the junction and decreases in width rearward of the junction.
Another aspect of the present invention involves a snowmobile comprising a body, a pair of skis disposed generally below a forward portion of the body and a drive arrangement disposed generally below a rearward portion of the body. The snowmobile slides on the pair of skis and is powered in at least a forward direction by the drive arrangement. At least one of the skis comprises a passage extending from a lower surface to an upper surface through the ski. The passage is capable of directing ice toward the drive arrangement during forward movement of the snowmobile.